I was practicng on `Rolling-Hash` on string.  When I checked out the following two problems:\n\n+ [1044. Longest Duplicate Substring](https://leetcode.com/problems/longest-duplicate-substring/)\n+ [1062. Longest Repeating Substring](https://leetcode.com/problems/longest-repeating-substring/)\n\nThe solutions both mention about using `rolling-hash` to optimize the string calcualtion. But One of them handles hash-collision, the other does not.\n\nSo I am confused about the criteria of handling `hash-collision`.\n\nThanks for your help.

I was practicng on Rolling-Hash on string.  When I checked out the following two problems:\n\n+ 1044. Longest Duplicate Substring\n+ 1062. Longest Repeating Sub